The default arrow should be displayed at times when the rest of the system may not be available (for example, at boot), so it is likely to be stored in a special place, for example, in the equipment itself.
The closest image to the default cursor is probably the "context menu", here:
/System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/HIServices.framework/Versions/A/Resources/cursors/contextualmenu/cursor_1only_.png
With some minor changes, you can probably turn this image into a whole arrow picture.
Most other cursors have images in WebKit, here:
/System/Library/Frameworks/WebKit.framework/Versions/Current/Frameworks/WebCore.framework/Resources/
Kevin grant
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